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Journal of Clinical Medicine Research

Original Article

Volume 10, Number 7, July 2018, pages 576-581

Characteristics and Factors Associated With the Mortality of Hypotensive Patients Attending the Emergency Department

Hypotension, defined as either a mean blood pressure (MBP) < 65 mm Hg, a systolic blood pressure (SBP) < 90 mm Hg or a > 40 mm Hg decrease in the SBP [1, 2], is associated with a high mortality rate of 8-15% [3] in patients presenting to emergency departments (EDs). When hypotension progresses to shock or circulatory failure, there is an imbalance between tissue oxygen delivery and oxygen consumption that results in signs of poor perfusion, end-organ dysfunction and, if untreated, death [4].

In the USA, approximately 5.6 million hypotensive patients per year are seen in EDs, representing 1% of all ED attendances [5]. The main causes of hypotension are infection, hypovolemic, cardiogenic, neurogenic, and drug induced hypotension. However, the etiological characteristics and mortality rates in patients who develop shock in the ED are not well described.

The rapid diagnosis and treatment of hypotension is important because if shock develops, it may become irreversible and delayed treatment is associated with an increasing mortality of 35-56% for cardiogenic shock, and 40-60% for sepsis-related shock [6]. Defining the clinical characteristics and epidemiology of hypotension are important to inform triage and management policies in EDs.

There are few data on the causes, clinical characteristic and prognosis of hypotension in the ED. We, therefore, set out to ascertain these and report the findings herein.

This was a retrospective cohort study of hypotensive patients presenting to the ED of Thammasat University Hospital (TUH) between June 1 and August 31, 2016. TUH is a tertiary referral center situated in the northern outskirts of Bangkok with 700 beds and sees approximately 45,000 patient ED visits per year.

The study was approved by Human Research Ethics Committee of Thammasat University, and funding was obtained from the Thammasat Research Fund.

The study inclusion criteria were one of: 1) an SBP < 90 mm Hg, 2) a mean arterial blood pressure (MAP) < 65 mm Hg, or 3) a decrease in SBP > 40 mm Hg from baseline [5, 6]. The exclusion criteria were patient who aged < 17 years old and/or who had an out of hospital cardiac arrest.

Using the hospital information system, all notes were retrieved of patients with a diagnosis of hypotension. Data were extracted using a standard case report form and included demographic data, major symptoms, serial pulse, blood pressure and oxygen saturation measurements, laboratory parameters, including serum lactate, clinical diagnoses and outcomes at 24 and 48 h. The SIRS criteria were used to select patients, comprising at least two of the following criteria: HR > 90/min, RR > 20/min, body temperature < 36 °C or > 38.3 °C, and white blood cell count > 12,000/µL or < 4,000/µL [2, 7]. We calculated the quick sequential organ failure assessment (qSOFA) score ranges from 0 to 3 with one point awarded for each of the following clinical signs: SBP ≤ 100 mm Hg, RR ≥ 22/min, and altered mental status from baseline [7].

The sample size was estimated (STATA v14, Stata Corporation, USA) according to the previous report [8] and our pilot study, and the 48 h mortality rate of patients with hypotension was 8%. Providing a power of 80% and two-side alpha of 0.05, the calculated sample size was 223.

Descriptive statistics are reported as frequencies, 95% confidence intervals, mean (standard deviation (SD)) and median (interquartile range (IQR)). Proportional data between groups were analyzed by Chi-squared or Fisher’s exact test; continuous data were analyzed by Student’s t-test or the Wilcoxon-Mann-Whitney U test for normally distributed and skewed data, respectively. Factors associated with mortality within 48 h were analyzed by multivariable logistic regression. All analyses (STATA v14) were two sided and a statistically significant P-value was defined as < 0.05.

A total of 9,000 patients were seen in the TUH ED during the 3 months study period. Of these, 250 patients presented with hypotension, including 17 patients who were referred to other hospitals. Therefore, the final number of included patients was 233. Patient’s characteristics are shown in Table 1. The mean age was 61.4 ± 20.2 years, and there was a slightly higher proportion (53.7%) of male patients.

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Table 1. Baseline Characteristics and Clinical Outcomes of 233 Hypotensive Patients

The majority of patients had an underlying disease (69.1%), including hypertension (40.3%) and diabetes mellitus (DM, 26.2%). Most patients (88.8%) had been brought to hospital by their families; the rest came by ambulance, and the emergency medical service (EMS, 11.2%). A minority of patients, 2.2%, were at the critical triage level, according to TUH triage criteria. The median times to receive initial IV fluids, to achieve an MAP ≥ 65 mm Hg, and admission times were 29 min, 103 min, and 21 h, respectively.

The chief complaints were fever (18.5%), dyspnea (16.7%), and abdominal pain (8.6%). On admission to the ED, the mean SBP was 78 mm Hg, the mean diastolic (DBP) was 48 mm Hg, the mean pulse rate was 96/min, and 7.3% of patients had an oxygen saturation ≤ 90%. The mean shock index (heart rate/SBP) and modified shock index (heart rate/MAP) were 1.3 and 1.7, respectively. Of patients, 36.5% had ≥ 2 of the SIRS criteria and 21.9% met qSOFA score ≥ 2. The most common cause of hypotension was infection (50.2%) followed by hypovolemia (40.8%). The initial median serum lactate concentration was 3.5 mmol/L (IQR 1.6 - 4.4).

The median volume of fluid required to achieve an MAP ≥ 65 mm Hg was 1,142 mL (IQR 500 - 1,500) and 27.0% of patients received a vasopressor. Of patients, 40.3% had recurrent hypotension, 16.7% of patients were intubated, and 8.2% died within 48 h.

By univariable analysis, the factors associated with mortality within 48 h are shown in Table 2. The main factors were: 1) being bed ridden, 2) initial pulse rate > 100 beats/min, 3) initial pulse oximetry ≤ 90%, 4) altered mental status, 5) qSOFA score ≥ 2, 6) diagnosis of shock, 7) total fluid in first hour ≥ 1,500 mL, 8) intubation, 9) recurrent hypotension, and 10) those who needed a vasopressor. By multivariable logistic regression, there were three independent factors associated with death ≤ 48 h (Table 3); these were initial pulse rate > 100 beats/min, diagnosis of shock, and recurrent hypotension.

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Table 2. Univariable Analysis of Factors Associated With 48 h Mortality in Hypotensive Patients

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Table 3. Multivariable Analysis of Factors Associated With 48 h Mortality in Hypotensive Patients

In our retrospective study, we have shown that hypotensive patients account for less than 3% of all ED attendances, but they suffered a 48-h mortality of just over 8% and half of those deaths were associated with a final diagnosis of infection.

The baseline characteristics of our ED patients presenting with hypotension were similar to those reported in previous studies, i.e. older patients with underlying morbidities [8-10]. Waiting times to see the doctor and receive treatment were 10 and 28 min, respectively, which compare favorably to the times reported by the US CDC in 2010 - 2011 of 10 and 30 min, respectively. Our ED is busy and sees some 45,000 patients per year and overcrowding and long waiting times are significant challenges we face.

The prevalence of hypotension in EDs varies depending on where the study took place and the definition used of hypotension. Moreover, definitions of sepsis and septic shock have evolved over time with changing definitions of hypotension and shock. Holler et al from Denmark reported an ED prevalence of hypotension of 1% with a 7-day mortality of 12% [1]; this contrasts with a higher rate of 19% reported by Jones et al whose patients suffered an in-hospital mortality of 8% [8].

Although the most common complaint was fever, it was only reported in a little under 20% of patients; interestingly a similar proportion also had a measured fever of ≥ 38 °C. This should alert physicians to a diagnosis of possible sepsis even if the measured temperature is within the normal range. In our series, 113 of 233 patients had sepsis according to qSOFA score, of which 45% had septic shock. This score has been accepted as a screening tool to identify patients who may have early sepsis in the EDs [7, 11].

We found that the qSOFA score was related to hospital mortality in the univariable analysis but it was not a significant factor in the multivariable analysis, which accords with Askim et al and Tusgul et al who found that the qSOFA failed to be a risk stratification tool for predicting 7- and 30-day mortality [12, 13]. The shock and modified shock index may be good markers of a patient’s hemodynamic status and have been found to be associated with increased mortality in the ED [14, 15]. We did not show that either index was a significant mortality factor. This difference could be explained by heterogeneity in patients’ characteristics and clinical settings among studies.

Within the first hour, the mean volume of isotonic crystalloid fluid resuscitation given to our patients was approximately 750 mL. This amount is in accordance to the survival sepsis campaign, which recommends fluid replacement of 30 mL/kg in the first 3 h [16].

The three independent factors associated with death within 48 h were initial pulse rate > 100 beats/min, shock diagnosis, and recurrent hypotension; these are consistent with the findings of Barfod et al who reported that the SpO₂, respiratory rate, SBP and Glasgow coma score were all significantly associated with in-hospital mortality [17]. Factors that we found to be unrelated to increased mortality include serum lactate level and shock index which contrast to a number of other studies [14, 18-22], and could be due partly to our heterogeneous population. Interestingly, a recent meta-analysis found that delayed antibiotic treatment was not associated with an increased risk of death in sepsis [22].

Our study had some limitations. This was a single hospital study with a relatively small number of patients. In addition, this was retrospective, with some incompleteness of data. Larger prospective studies are needed to validate our findings, which could contribute to developing a predictive score of mortality among these patients.

Hypotension is a common problem in the ED, with sepsis being the most common cause. Our 48-h mortality rate of all causes hypotension was high. In our setting, initial pulse rate > 100 beats/min, diagnosis of shock, and recurrent hypotension were risk factors for death. This knowledge should help ED personals to better triage these patients, and initiate treatment promptly.

Acknowledgments

We thank Dr. Bob Taylor, Dr. Sith Siramolpiwat and Dr. Sumet Kongkiatpaiboon for proof-reading and reviewing the manuscript.

Funding Support

The research was supported by Thammasat Research Fund.

Conflict of Interest

None.

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Journal of Clinical Medicine Research is published by Elmer Press Inc.